The present invention relates in general to venetian blind constructions and, in particular to a new and useful venetian blind construction which includes mechanisms for setting the blinds at particular angles when the venetian blind is opened or closed.
Prior art venetian blinds are usually designed so that, by turning the drive shaft to lift the slats (gathering), the slats are mostly pivoted into a substantially horizontal, open position, while a turning in the opposite direction causes their pivoting into a mid position between open and closed, (e.g. 45.degree. ) which is frequently called the working position. A fully closing position (substantially vertical) of the slats is to be reached only upon completely lowering the blind. Prior art constructions of this kind are mostly complicated and therefore, susceptible to mechanical problems. Since the setting straps form a non-positive slipping clutch with the surfaces they contact, fully or partly open slats may easily be misadjusted, for example by the action of the wind. Frequently the arrangement is such that upon winding off the last turn from the wind-up drum, the lifting strap releases a spring loaded coupling member intended to cause the slats to pivot into their closing position. Prior art designs of this kind have the disadvantage that, for example, the slats come to rest upon an obstacle, any slackening of the setting strap on the drum leads to an undesirable premature release of the coupling member. With a further mechanical drive of the blind a mostly unavoidable overrun of the motor may cause the coupling member, in an effective position, to move farther, which may result in damage.